Originally Posted by Ajax

1-Arrival rates are determined by several factors, with the main one being the weather. Strong winds will lower arrival rates because of extra compression on final means we need extra spacing buffer on final to account for that. Low ceilings means visual separation may not be possible, and we running bare minimum IFR separation without the ability to use visual to prevent a compression error is too risky. Other reasons are runway configurations, runway closures on secondary (overflow) runways, departure demand, special activities (VIP movement, law enforcement operations in progress, etc). I've even seen controller staffing (or lack of) be a factor for a lower rate, although the FAA will go to extremes to avoid citing that as a reason (even if its true).

2-Even if technically the required minimun IFR separation is the same, once the ceilings/visibility drops, and we (and the tower) lose the ability to use visual separation, we need a bigger buffer on final to avoid compression "deals".

3-Many controllers are reluctant to issue a visual unless you're already straight in on final behind the traffic at a compatible distance and speed.When a controller issues a "follow that traffic, cleared visual approach rwy 22L" clearance, he is passing to you the burden of separation between your aircraft, and the one you're following, but is giving you control to manouver the aircraft as you see fit to maintain separation, and make an approach to the runway behind that traffic. The problem with this is that not every pilot will react exactly the same way, and while some will stay nice and tight behind the traffic, others give themselves and extra buffer, and may delay a turn from base to final, or make a very wide turn. If there is not much going on it doesn't matter much, but if its very busy, that may impact the traffic I have behind you.

Also, anyone and their uncle can run a visual approach final, as the need for good timing, precision vectors and speed control is lessened, since we're passing that to you. It is considered "harder" or more "skilled" to run a nice tight, even spaced IFR final, and thus this is how we run the final when we're training new controllers. Not saying we would never run visuals, because we do, but running visual approaches all the time is a crutch, and when the proverbial sh*t hits the fan, and the wx goes down, you better be able to handle it. To give you a comparison you can relate...would you train your pilots to always depend on autopilot, and autolandings?

4- Although I don't know the exact number, a great % of JFK traffic is heavy jets/b757's that require wake turbulence separation. EWR and LGA have less heavy jet traffic so its not unusual to see our finals tighter than JFK's. Having said that I'm going to repost something here that I posted on another forum while I was trying to answer a similar question, but using CLT instead of JFK.

The original question was " why does CLT run 5 mile spacing on final to landing only runways. While LGA, ORD, etc run 3 miles."

My reply was:

"I don't know the CLT operation, so I wont coment on their specifics, but I think I know where he's going with that questioning, and I'll try to answer with what happens here @ N90, and in particular my area (EWR)

Not all controllers are created equal, just like not all pilots are created equal. Some controllers are just....good for lack of any fancy words, and can run a very tight final. Others may not be that sharp, and run extra spacing for "safety". There are other factors to add to those 2 categories. There are controllers that tend to be a bit more aggressive, and there are some that, even if they have the "skills" to run a very tight final, they prefer to be conservative, and build in a little extra spacing buffer.

It all comes down to local culture. In my area, the "aggressive" controller tends to be more the norm than the exception (but we do have exceptions), and thus our finals tend to be pretty tight most of the time. It is engrained in the sector culture to run traffic this way and trainees are trained in this matter, supervisors encourage it, etc. In other places, the predominant type is the other, and thus people are trained to run bigger buffers.

I've visited several other facilities, and also noticed what he's talking about. I've seen other places run 5 mile final on everything, and do like 6 or 7 behind heavy's."

5-Windshear reduces the arrival rates because the potential for go arounds is higher. Every go around becomes .....an extra arrival.

6-The EWR downwind is super wide because departures out of EWR, TEB, MMU, and CDW need a climbout corridor to be able to get on top of the arrivals. The boundary line goes from MMU to CDW to TEB, so that is why you normally get vectored to stay on the outside, and make the wide turn. In addition, when its busy, the downwind can, and often extend all the way to SAX and is not uncommon to turn base over 4N1 (Greenwood lake airport).


As for the other question regarding departures staying @ 17000 for long distances. The Liberty sector (the area that takes all the departures from all the airports and gets traffic over all the different fixes in trail for ZNY) only "owns" up to 17000. Above them is ZNY, and they have inbound JFK arrivals descending to FL 190, so until Liberty hands you off to the center, and they have you cleared of any inbounds, you're going to be stuck below them. Doesn't happen all the time, but some airports (like HPN) have greater distances to fly, and will be leveled at 17000 for longer. Just the nature of the airspace.